Effects of organic mineral fertiliser on heavy metal migration and potential carbon sink in soils in a karst region

Heavy metal pollution in karst mountainous area of Guizhou has spread due to the long-term exploitation of mineral resources and the improper disposal of environmentally hazardous waste. Heavy metals are characterised by non-degradation, strong toxicity, and constant accumulation, posing a grave threat to karst mountain fragile soil ecosystem. To reduce the harm caused by heavy metal pollution and damage to agricultural products, research was undertaken on the basis of previous work by simulating pot experiments on pak choi cabbage(Brassica rapa chinensis)planted in Cd-contaminated soil: different amounts of organic mineral fertilisers(OMF) compared with chemical fertiliser(CF) were used and by detecting the amount of heavy metal in the mature vegetable, a better fertilisation strategy was developed. The results showed that the Cd content in vegetables grown with CF was 23.70 mg/kg,while that of vegetables grown with OMF and bacterial inoculant was the lowest at 15.13 mg/kg. This suggests that the use of OMF and microbes in karst areas not only promotes plant growth but also hinders plant absorption of heavy metal ions in the soil. In addition, through the collection of pot leachate, the detection of water chemistrycharacteristics, and the calculation of the calcite saturation index, it was found that the OMF method also induces certain carbon sink effects. The results provide a new way in which rationalise the use of OMFs in karst areas to alleviate soil heavy metal pollution and increase soil carbon sequestration.

Interactions between Soil Characteristics, Environmental Factors, and Plant Species Abundance: A Case Study in the Karst Mountains of Longhushan Nature Reserve, Southwest China

The ability to manage and restore plant communities in the face of human-induced landscape change may rely on our ability to predict how species respond to environmental variables.Understanding this response requires examining factors or their interactions that have influence on plant and resource availability.Our objective was to analyze the relationships between changes in plant abundance and the interaction among environmental habitat factors including soil, geological(rock type), and other environmental variables in the Longhushan karst mountains ecosystem.Species density and dominance were examined using ANOVA, ANCOVA,and Generalized Linear Models to establish the single or combined effects of these groups of factors.The results showed that trends in abundance were mainly affected by rock type(related to the percentage content of dolomite and calcite), soil characteristics in association with topography.Both plant indices were higher in dolomite dominated areas and varied positively with moisture, and elevation, but negatively with organic matter, while density also increased with slope degree.The results demonstrate that significant variations in species abundance was produced with the combination of variables from soil, geological, andenvironmental factors, suggesting their interaction influence on plants.We postulate that spatial variations in plant abundance in karst ecosystem depends on the carbonate rock type in addition to water and nutrient availability which are mainly controlled by topography and other factors such as soil texture and temperature.The study suggests that in karst areas carbonate rock type, in addition to local environmental variables, should be taken into account when analyzing the factors that have impact on plant communities.

Characteristics and distributions of humic acids in two soil profiles of the southwest China Karst area

Characteristics and distributions of humic acid(HA) and soil organic matter(SOM) in a yellow soil profile and a limestone soil profile of the southwest China Karst area were systematically investigated to reveal their evolutions in different soils of the study area. The results showed that characteristics and distribution of SOM along the two soil profiles were notably different. Total organic carbon(TOC) contents of soil samples decreased just slightly along the limestone soil profile but sharply along the yellow soil profile. TOCs of the limestone soils were significantly higher than those of the corresponding yellow soils, and C/N ratios of SOMs showed a similar variation trend to that of TOCs, indicating that SOM can be better conserved in the limestone soil than in the yellow soil. The soil humic acids were exhaustively extracted and further fractionated according to their apparent molecular weights using ultrafiltration techniques to explore underlying conservation mechanisms. The result showed that C/N ratios of HAs from different limestone soil layers were relatively stable and that large molecular HA fractions predominated the bulk HA of the top soil, indicating that HA in the limestone profile was protected while bio and chemical degradations were retarded. Combined with organic elements contents and mineral contents of two soils, weconcluded that high calcium contents in limestone soils may play a key role in SOM conservation by forming complexation compounds with HAs or/and enclosing SOMs with hypergene CaCO_3 precipitation.

Hazards and Landscape Changes(Degradations) on Hungarian Karst Mountains Due to Natural and Human Effects

In order to study the karstological processes within the karst ecological system,the geohazards and degradation of karst landscapes on the karst areas of the Bakony mountains(Hungary),we investigated the abiotic elements of the environment,soil and cover deposits,erosion soil decay;the changes in the quantity and quality of karst waters:contamination at swallow holes,contamination of karst springs;and the biogenic factors:surface vegetation coverage by the corine land cover method,plant-ecological examinations,qualification of surface waters with the help of biological water labeling.We recognized that the increasing human activities during the past few centuries have had significant impact on the investigated landscapes of karst areas because of their spatial sensitivity.In the scope of our research we concluded that the landscape changes due to natural and human effects can vary strongly on the different karst areas.These differences can arise from the climatic and geomorphologic situation,the coverlayer's qualities,etc.,but primarily from the different utilization of the investigated karst areas(e.g.the intensity,characteristics and territorial extension of utilization).On the spot investigation we detected traces of new and fast geomorphological processes(gully formation,landslides,collapses,new sinkhole development) and landforms(sinkholes,gullies,swallow holes),which are clear evidences of the effect of climatic changes.

西南岩溶区果园土壤—作物系统重金属元素迁移特征与污染评价

【目的】分析西南岩溶地区地质高背景下土壤—作物系统的重金属迁移富集关系及其潜在生态风险,为岩溶区土壤合理开发利用和粮食安全生产提供科学依据。【方法】选取广西较典型的岩溶区果园和撂荒地作为研究区,同时采集不同母质的土壤进行对比,对果园和撂荒地内植物的根、茎、叶、果实及土壤剖面(0~100 cm)中的8种重金属元素[镉(Cd)、铬(Cr)、砷(As)、汞(Hg)、铅(Pb)、铜(Cu)、锌(Zn)和镍(Ni)]含量进行研究,并分别采用单因子污染指数、地累积指数、生物富集系数及相关分析等方法对土壤及作物的生态风险进行评价。【结果】研究区土壤中重金属元素Cd、Cr、Cu、Pb、Ni和Zn含量平均值均超广西土壤元素背景值,其中,Cd和Zn含量分别是广西土壤元素背景值的7.7和5.4倍。地累积指数结果表明,果园剖面土壤的Cd存在中度至重度污染,Zn的最大值存在中度污染;撂荒地剖面土壤的Cd存在中度污染,Zn存在无污染至中度污染。果园土壤剖面中Cd、Cu、Ni和Zn 4种元素最大迁移率均出现在50~60 cm处,撂荒地土壤中Ni和Cd元素最大迁移率出现在30~40 cm处,Cu和Zn元素最大迁移率则出现在60~80 cm处。果园和撂荒地土壤的Cd活化率最高,具有较强活性。果园中7种重金属元素的作物污染指数排序为Pb(22.09)>Ni(20.84)>Zn(3.24)>As(2.77)>Cr(1.43)>Cu(0.21)>Cd(0.01)。比较作物根、茎、叶和果实的生物富集系数,发现所有元素含量均在根系部位最大;果实中As元素的生物富集系数最高,为0.07。除As和Pb 2个元素外,其他元素(Cu、Cd、Zn、Ni和Cr)的生物富集系数最小值均出现在果实。研究区内土壤和果实中同一种重金属元素含量之间无显著相关性(P>0.05),即土壤重金属元素含量不会影响作物重金属元素含量。【结论】研究区土壤中Cd和Zn的超标率较高,存在Cd污染现象;与土壤相比,研究区作物果实中Cd和Zn的生物富集系数总体较低,表明研究区重金属元素总体表现出高含量、低活性和生态低风险的特点。

A numerical simulation study on the evolutionary characteristics of the damage process of karst soil cavity under positive pressure effect

Positive pressure effect is the result of rapid urban development in recent years,which leads to over-exploitation of karst groundwater,coupled with the emergence of extreme weather(such as heavy rainfall,the increase in the duration of heavy rainfall),leading to the sharp rise of karst water level,the gas in the karst cavity can not be discharged in time to form a high positive pressure in the soil cavity and promote the destruction of the soil layer,which then induces a series of phenomena,such as karst subsidence.As a new collapse mechanism,the positive pressure effect causes geological disasters that seriously affect the safety of people's lives and properties in karst regions.In order to study the damage characteristics and evolution characteristics of karst soil cavities under positive pressure effect,this study is based on the ASCII text provided by FLAC itself,and the orthotropic simulation computation compilation program,which realizes the finite element analysis in FLAC3D,and focuses on the inhomogeneous change of soil displacement,redistribution of stresses,and plastic damage of karst soil cavities in different evolution stages under the action of positive pressure,and summarizes the characteristics and laws of stress,strain and damage in plastic zone of karst soil cave at different stages of evolution.The results will play a positive role in further investigating the potential mechanical effects,development mechanism and critical warning conditions during the evolution of covered karst soil caves,and also have important scientific research value in deepening the theory of prevention and control of collapse disasters in covered karst soil caves.

重庆岩溶地质高背景区土壤-农作物系统重金属累积特征及影响因素

为了揭示重庆岩溶地质高背景区土壤-农作物系统中重金属的迁移累积特征,选择在重庆市南部典型岩溶区,系统地采集大宗农作物(水稻、玉米和红薯)及其耕层土壤84组,分析测定农作物及耕层土壤中重金属砷(As)、镉(Cd)、铬(Cr)、铜(Cu)、汞(Hg)、镍(Ni)、锌(Zn)含量及理化性质,采用地统计、生物富集因子及皮尔逊相关系数分析等方法,开展重金属元素在重庆岩溶地质高背景地区土壤−农作物系统中累积特征及影响因素。结果表明,研究区水稻田、玉米地和红薯地耕层土壤重金属平均含量均高于重庆市和全国表层土壤背景值,呈现不同程度的积累,其中Cd元素富集现象较为突出。依据GB 15618-2018和GB 2762-2017,耕层土壤种Cd超标率达41.59%,水稻、玉米和红薯中Cd超标率分别为5.89%、6.25%和5.56%,显示出岩溶地质高背景区虽然土壤中重金属含量总量高,但生物有效性较低。相关分析显示,土壤-农作物系统Cd等重金属含量主要受土壤pH、土壤质地和土壤中铁锰氧化物影响。

溶岩与非溶岩地区隧道排水系统堵塞机理

岩溶与非岩溶地区隧道排水系统频繁发生堵塞灾害。溶岩地区排水系统堵塞物质主要为白色碳酸钙(CaCO_(3)),而非溶岩地区排水系统堵塞物质为黑色土颗粒。以法国Meyssiez隧道排水系统堵塞灾害为依托,通过测试隧道围岩孔隙比e和地下水电导率EC,分析了岩溶地区隧道排水系统的堵塞机理。试验结果表明:(1)溶岩地区排水系统堵塞主要由以下过程引起:(1)雨水入渗地下后,溶解了围岩内部的碳酸钙,形成Ca^(2+)和HCO_(3)^(-)离子;(2)含有Ca^(2+)和HCO_(3)^(-)离子的地下水通过排水孔流入隧道内部的排水系统。由于气温和气压等外部因素改变,Ca^(2+)和HCO_(3)^(-)离子反向沉积形成固态CaCO_(3)结晶,最终引发排水系统堵塞;(2)非溶岩地区隧道排水系统堵塞灾害由以下过程引起:(1)地下水流作用引发围岩内部细小土颗粒迁移流失;(2)流失的细小土颗粒通过排水孔进入隧道内部排水系统,而后逐步堆积,最终引发排水系统堵塞。

岩溶土壤系统对空气CO_(2)的吸收及其对陆地系统碳汇的意义——以桂林丫吉村岩溶试验场的野外观测和模拟实验为例

以桂林丫吉村岩溶实验场为例 ,对湿润亚热带岩溶土壤系统进行了土壤植被系统CO2 浓度变化、土壤有机质分解的CO2 产生等野外观测以及实验室土壤灰岩土柱系统模拟实验。实验表明在土壤地球化学条件的控制下 ,岩溶土壤系统存在着对空气CO2 的显著吸收效应 ,其值可达 2 2～ 130 g/ (m2 ·a) ,并以此为依据估算了中国岩溶土壤系统对大气的碳汇约为 4× 10 13g/a。因而揭示了岩溶土壤系统可能是十分重要的陆地碳汇 ,在讨论全球碳汇饱和问题中必须重视这一碳汇的变化。

表层带岩溶作用:以土壤为媒介的地球表层生态系统过程——以桂林峰丛洼地岩溶系统为例

作者基于在桂林丫吉村岩溶试验场的长期、系统观测及有关实验研究进展,从影响岩溶作用的土壤化学因素、土壤CO2 及土壤有机碳行为等方面论证了土壤对于表层带岩溶作用的媒介及驱动意义,提出岩溶地球化学过程涉及到土壤中Ca2+ 的移出及交换释放,土壤CO2对系统空气CO2 浓度及HCO3- 排释的控制,并指出土壤有机碳是岩溶作用碳转移的重要媒介。作者认为表层带岩溶系统的发育演进为石质岩溶→生物岩溶→土壤岩溶→生态系统岩溶,因而表层带岩溶作用是以土壤为媒介的表层生态系统过程。

岩溶动力系统对典型石灰岩土肥力特征的影响

碳酸盐岩 (Ca CO3)— CO2 (气 )—水 (H2 O)三相组成的岩溶动力系统 ,通过驱动环境元素的迁移 ,可影响土壤的基本性质及营养元素的形态和转化。一方面土壤盐基离子 (Ca、Mg、K、Na)的大量淋失 ,另一方面岩溶作用产生的富钙环境使土壤体系中盐基获得补充 ,形成偏碱的土壤环境 ,并因此使石灰岩土的阳离子交换量和有机质含量较高 ,但也降低了土壤铁、锰、磷、锌等元素的有效性 ,最终对土壤肥力特征及演变产生深远的影响。

喀斯特石漠化过程中植被演替及其对径流水化学的影响

通过对贵州中部喀斯特地区进行植被调查以及土壤和径流样品的分析,探讨石漠化过程中植被演替及其对径流水化学组成的影响。结果表明:喀斯特石漠化后,土壤出现粘质化,有机质含量急剧下降,土壤毛管孔隙度下降,干旱季节表层和次表层土壤的含水量明显减少,改变了生态系统的水分运动规律。喀斯特地表径流中离子浓度的大小排序为HCO3->SO42->Ca2+>Mg2+>K+、NO3-、Cl->Na+>NH4+>PO43-,地表径流水化学类型以HCO3-Ca型为主;随着石漠化程度的增加,地表径流中PO43-输出量明显增加,其次是Ca2+、NO3-,这部分养分的流失造成土壤养分水平下降,同时影响受纳水体的环境质量。地下径流离子组成与地表径流总体相似,但HCO3-、Ca2+、Mg2+的含量高于地表径流,而K+、NH4+的含量低于地表径流;石漠化发生后,地下径流中HCO3-、Mg2+浓度明显减少,岩溶作用减弱,而NH4+、NO3-浓度明显增加,对地下水质产生一定的影响。

岩溶石山区石灰土改良方法及对比试验研究——以广西平果县龙何屯为例

本文以广西平果县龙何屯为例,在系统分析石灰土的特征和障碍因素层次的基础上,探讨石灰土改良的原理和方法。以岩溶动力系统原理为指导,采用平衡施肥和秸秆还土改良石灰土,进行对比试验研究。试验结果表明,平衡施肥改良石灰土,不仅增加作物产量和经济效益,而且提高作物的秸秆产量和残茬量,为进一步改良石灰土提供物质基础。作物秸秆还土改良石灰土具有较高的增产效果和改土培肥效果,并受岩溶作用的制约。不同的秸秆搭配类型和还土方式导致不同的岩溶作用强度,进而导致土壤改良效果的显著差异。各方案改良效果与岩溶作用强度呈显著的正相关,在秸秆搭配类型上,表现为:玉米秸秆+黄豆秸秆+农家肥>玉米秸秆+黄豆秸秆>玉米秸秆+氮肥>玉米秸秆;在还土方式上,表现为:翻压>覆盖。

广西亚热带岩溶地区石灰性土壤钾素特征研究

试验研究广西亚热带岩溶地区石灰性土壤K素特征结果表明．该区农田生态系统中棕色石灰土速效钾含量和速效钾可释放量能较好地反映土壤对当季作物的供K能力；当土壤速效钾含量降至30～32mg／kg时，作物难以吸收土壤中的K素，严重限制作物生长；土壤主要养分限制因子为土壤缺K，且P、S、B、Zn不足；棕色石灰土缓效钾含量和缓效钾可释放量不能正确反映土壤对当季作物的供K能力，但能较正确反映土壤的持续供K能力。施K有利于维持土壤K素平衡，通过增施K肥获得作物高产可行。

微生物及其碳酸酐酶对岩溶土壤系统钙镁元素淋失的影响

通过室内模拟土壤-灰岩岩溶系统,对不同微生物处理条件下的土柱进行降水淋滤,系统监测了淋出液的pH、电导率、Ca2+、Mg2+以及碳酸酐酶(CA)活性。结果表明,微生物对该模拟系统Ca、Mg元素迁移有较大促进作用。扫描电镜显示,埋入经微生物处理土柱的试片表面较对照(未埋入土柱和埋入灭菌土柱的试片)有明显侵蚀现象。另一方面,各处理的淋出液中均检测出不同程度的CA活性,说明土柱中的微生物产生了胞外CA并被淋出。相关分析表明淋出液中CA平均活性与Ca2+总淋失量之间存在较好的正相关关系,说明CA是影响Ca元素淋失的主要因素。对其进行深入研究将有助于解释生物岩溶的机理。

土壤-灰岩岩溶系统中水文地球化学动力学过程模拟及其意义

在实验室模拟了土壤－灰岩岩溶系统，对降水淋滤下元素地球化学动态进行了系统监测。结果表明，岩溶作用使土壤中易移动性组分淋溶，Ｃａ^（２＋）、ＨＣＯ_３~－的淋出动态表现为开始的快速下降和随之的平衡两个淋出阶段，淋出量与土壤中水溶性Ｃａ、可氧化有机质的含量有关。土壤对ＨＣＯ_３~－的淋出与排释有促进作用。这种动力学特征对解释岩溶沉积古记录和岩溶作用的大气ＣＯ_２汇效应具有重要意义。

岩溶系统土壤吸释CO_2作用及其环境意义──以桂林丫吉村岩溶试验场为例

野外监测土壤CO2释放结果表明：土壤CO2释放量晴天高于雨天；洼地、垭口土壤CO2释放量高于坡地土壤CO2释放量；试验场土壤CO2年释放量在1057．8t（1．763kgm-2），与552．6t（0，921kgm-2）之间，估算值为810．0t（1．35kgm-2）。野外溶蚀试验结果表明：试验场岩上作用过程年吸收CO2量为13．08t；岩溶系统年吸收CO2量为61．73t。土壤是温室气体（CO2）的重要贡献者，岩、土、水系统是环境变化的缓冲系统，植树造林（石山改造）是改善岩溶地区生态环境的决定性举措。

喀斯特地区土地石漠化风险及评价指标体系

土地石漠化是西南喀斯特地区一种突出的生态环境问题,是西南喀斯特地区经济发展与生态建设中所面临的特殊的地域性环境问题,也是西南喀斯特地区实现全面可持续发展的主要障碍因素之一。在参考国内外相关研究成果的基础上,根据对石漠化概念的内涵及特点的分析,构建了石漠化概念模型,论述了土地石漠化与基底环境的基本反馈响应机制。根据模型将风险压力分为干扰、累积、演替、破碎这4大类,分析提取土地石漠化风险因子,按"压力—状态—响应"模型对土地石漠化风险因子进行了分级,初步建立了喀斯特地区土地石漠化风险评价指标体系。

岩溶系统中土壤氮肥施用对岩溶碳汇的影响

有资料显示陆地碳酸盐岩风化消耗大气CO2的碳通量与世界森林碳汇通量量级相当。但农业地区过量施用氮肥形成的硝酸对碳酸盐岩的溶解会减弱岩溶碳汇效应,其量可达到7%~38%,而适量施用氮肥在增加农作物产量的同时,能降低土壤C/N比,增加土壤微生物活性,促进有机物料分解,从而提高土壤CO2浓度,提高土下碳酸盐岩的溶解速率。因此,要从两方面分析岩溶系统中土壤氮肥施用对岩溶碳汇效应的影响。同时,岩溶区碳酸盐岩风化形成的土壤具有较高的pH值及盐基饱和度,对H＋有较强的缓冲作用,可能是导致自然条件下,河流中溶解无机碳（DIC）与水体中钙、镁等离子并不守恒的原因之一,因此,运用端元法可能过高估算了硝酸对碳酸盐岩的溶解量。岩溶区土壤环境中硝化作用产生的硝酸到底多少能对碳酸盐岩产生溶蚀,并影响到岩溶碳汇效应还有待研究。应结合土壤本身的特性及河流生物地球化学过程,综合研究不同施氮水平、土壤硝化产酸及其影响下的土下碳酸盐岩溶解及碳汇效应过程,客观评价岩溶区土壤氮肥施用对岩溶碳汇的影响,并寻求适宜氮肥施用量及促进岩溶碳循环,提高岩溶碳汇效应的技术方法。